US3617917A - Converging solid-state laser element for high-power output use - Google Patents

Converging solid-state laser element for high-power output use Download PDF

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Publication number
US3617917A
US3617917A US877238A US3617917DA US3617917A US 3617917 A US3617917 A US 3617917A US 877238 A US877238 A US 877238A US 3617917D A US3617917D A US 3617917DA US 3617917 A US3617917 A US 3617917A
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Prior art keywords
laser element
axis
refractive index
converging
end surface
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Expired - Lifetime
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US877238A
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English (en)
Inventor
Teiji Uchida
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Nippon Selfoc Co Ltd
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Nippon Selfoc Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/0602—Crystal lasers or glass lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/17—Solid materials amorphous, e.g. glass

Definitions

  • the spot size at the output end of the element can be made greater than the incident spot size at the input end surface.
  • the present invention relates to a solid-state laser element and, more particularly, to an improved rod or fiberlike solidstate laser element having light-converging capability whose refractive index observed in the plane normal to its axis is highest at the axis and gradually decreases toward the surface.
  • Solid-state lasers for continuous oscillation use have recently been developed, in which the output power obtained is as high as that obtained from conventional gas lasers.
  • An activating oxide is doped in at least a portion of the total length of the element.
  • a glass laser element of this type has a refractive index distribution given approximately by the expression:
  • n N( l-iar), l
  • N the refractive index at the axis of the element
  • r the radial distance from the axis
  • a is a constant
  • n the refractive index at a distance r measured from the axis.
  • an ultrahigh speed light pulse train can be amplified without distortion when a laser amplifier is fonned of a converging glass laser element
  • the converging glass laser element is subjected to the optical excitation necessary for achieving oscillation and amplification, the excitation light rays irradiating the element from the periphery of the element are concentrated onto the axial portion of the element, as a result of the above-defined refractive index distribution. Since the laser light beam generated by the element through the excitation light travels therethrough in the axial direction oscillating about the axis, the efficiency of the excitation is quite high.
  • the converging glass laser element is equivalent to a medium having the refractive index distribution defined in equation (1). Therefore, according to the analysis given in the Miller article, the spot sizes W (diameter) of the input and output light beams of the fundamental mode are given by in 1/2 W (111V) where he is the wavelength of light in free-space.
  • a light beam having a spot size defined by equation (2) incident upon the converging glass laser element is amplified and arrives at the output end surface with the same spot size. Since the power of the light beam is limited by its spot size, the intensity of the laser output is also limited. In other words, saturation occurs in the vicinity of the output end surface.
  • the spot size at the output end surface of the converging glass laser element is difi'erent from that at the input end surface.
  • the larger spot size at the output end allows for higher output power without saturation.
  • FIG. 1 is a longitudinal cross-sectional view of the solidstate laser element of the invention illustrating the relation between the input, output and excitation light beams within the element; and FIG. 2 schematically shows the variation of the spot size of the light beams transmitted through the laser element of FIG. 1.
  • a glass laser element 1 of the present invention is shown in the shape of an elongated truncated cone having parallel end surfaces 3-3' and 4-4 normal to the longitudinal axis 20-20 of the element.
  • N(z) and a(z) monotonically decrease as z increases.
  • the reference numeral 2 denotes the laser-activating ions necessary for sustaining laser oscillation which may be, for example, neodymium ion Nd and a sensitizer, which may be, for example, uranium ion U, which are uniformly distributed in the glass laser element 1.
  • the spot size of this light beam is made approximately equal to the specific spot size determined by the refractive index distribution at the input end surface 3-3'.
  • laser element 1 Since laser element 1 has a converging action due to the refractive index distribution defined by equation (3) or, in other words, due to the high-refractive index at the axis and thus rather low refractive index at the outer periphery of the element, the incident light beam 11 is axially transmitted through the element and oscillates about the axis.
  • the refractive index of the glass laser element 1 decreases in the z axis direction.
  • the converging action is therefore weakened as the laser beam travels toward the right in FIG. 1 along the z axis. Therefore, the cross-sectional area of the light beam is enlarged as it approaches the output end surface 4-4, as shown by reference numeral 11' in FIG. 1.
  • the refractive index distribution is given along the z axis as has been described above, so that the light beam does not deviate from the periphery of the element 1, the light beam incident upon the input end surface 3-3' is transmitted therethrough, as shown by 11' in FIG. 1, oscillating about the axis and colliding with the laser-active material 2, and then emerges from the output end surface 4-4. With the exciting light beam 5 concentrated on the glass laser element 1, the input light beam emerges from the element 1 as the output beam 11".
  • the spot size at the output end surface is apparently large as compared with that at the input end surface.
  • the saturation value determined by the power density of the light beam at the output end surface 4-4 can be increased to obtain a relatively larger output power than could be obtained in the prior art laser elements of this type.
  • F lG. 2(a) schematically shows the broadening of the spot size of the laser element of the invention.
  • the shape of the laser element may be other than an elongated truncated cone.
  • a cylindrical shape for the laser element for example, as shown in FIG. 2(b), may be effective if only one of a(z) and N(z) decreases with z.
  • the host material of the laser element is assumed to be glass in the above description, any suitable transparent material such as plastic, can be used instead of glass to form the element.
  • a glass laser element capable of producing a high power output can be realized.
  • a solid-state laser element comprising a transparent body of host material including laser-active material substantially uniformly distributed in at least a portion of its entire axial length, said element having an input and an output surface, wherein the refractive index n of the host material at a point of distance r from the axis of said body is defined substantially by an expression n N( l-lafl), where N is the refractive index at said axis, and a is a positive proportional coefficient decreasing monotonically along said axis from said input surface to said output surface.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Lasers (AREA)
US877238A 1968-11-16 1969-11-17 Converging solid-state laser element for high-power output use Expired - Lifetime US3617917A (en)

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JP8367268 1968-11-16

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US (1) US3617917A (cg-RX-API-DMAC7.html)
DE (1) DE1955963A1 (cg-RX-API-DMAC7.html)
FR (1) FR2023459A1 (cg-RX-API-DMAC7.html)
GB (1) GB1269103A (cg-RX-API-DMAC7.html)
NL (1) NL6917219A (cg-RX-API-DMAC7.html)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3729253A (en) * 1971-05-28 1973-04-24 Western Electric Co Optical system comprising a single element having a continuously varying index of refraction
US3916182A (en) * 1972-08-21 1975-10-28 Western Electric Co Periodic dielectric waveguide filter
US4025157A (en) * 1975-06-26 1977-05-24 The United States Of America As Represented By The Secretary Of The Navy Gradient index miniature coupling lens
US4053205A (en) * 1976-07-30 1977-10-11 Bell Telephone Laboratories, Incorporated Optical fiber having reduced dispersion
US4053204A (en) * 1976-07-30 1977-10-11 Bell Telephone Laboratories, Incorporated Optical fiber having reduced dispersion
US4076380A (en) * 1976-10-28 1978-02-28 Bell Telephone Laboratories, Incorporated Graded index optical fiber
WO1992010014A1 (en) * 1990-11-30 1992-06-11 Nkt A/S A method and apparatus for amplifying an optical signal
US5287373A (en) * 1992-08-17 1994-02-15 Alliedsignal Inc. Gradient doped solid state laser gain media
US6624925B2 (en) * 2001-03-13 2003-09-23 Textron Systems Corporation Optical amplifier employing an active doped unitary amplifier
US6937636B1 (en) * 1999-09-27 2005-08-30 The Regents Of The University Of California Tapered laser rods as a means of minimizing the path length of trapped barrel mode rays

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3083123A (en) * 1960-06-01 1963-03-26 Gen Electric Magnesia alumina spinel articles and process of preparing same
US3320114A (en) * 1963-07-31 1967-05-16 Litton Prec Products Inc Method for lowering index of refraction of glass surfaces
US3372972A (en) * 1962-07-30 1968-03-12 Trw Inc Optical beam deflector
US3434774A (en) * 1965-02-02 1969-03-25 Bell Telephone Labor Inc Waveguide for millimeter and optical waves
US3533013A (en) * 1967-03-23 1970-10-06 Elton Ind Inc Optical maser having means for concentrating the pumping light energy in the central portion thereof

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3083123A (en) * 1960-06-01 1963-03-26 Gen Electric Magnesia alumina spinel articles and process of preparing same
US3372972A (en) * 1962-07-30 1968-03-12 Trw Inc Optical beam deflector
US3320114A (en) * 1963-07-31 1967-05-16 Litton Prec Products Inc Method for lowering index of refraction of glass surfaces
US3434774A (en) * 1965-02-02 1969-03-25 Bell Telephone Labor Inc Waveguide for millimeter and optical waves
US3533013A (en) * 1967-03-23 1970-10-06 Elton Ind Inc Optical maser having means for concentrating the pumping light energy in the central portion thereof

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Kawakami et al. Article in Proceedings of the IEEE Dec. 1965 pgs. 2148 and 2149 cited copy in 350/96 (WG) *
Miller Article in Bell System Technical Journal Vol. 44 No. 9 Nov. 1965 pgs. 2017 2030 cited copy in 350/96 (WG) *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3729253A (en) * 1971-05-28 1973-04-24 Western Electric Co Optical system comprising a single element having a continuously varying index of refraction
US3916182A (en) * 1972-08-21 1975-10-28 Western Electric Co Periodic dielectric waveguide filter
US4025157A (en) * 1975-06-26 1977-05-24 The United States Of America As Represented By The Secretary Of The Navy Gradient index miniature coupling lens
US4053205A (en) * 1976-07-30 1977-10-11 Bell Telephone Laboratories, Incorporated Optical fiber having reduced dispersion
US4053204A (en) * 1976-07-30 1977-10-11 Bell Telephone Laboratories, Incorporated Optical fiber having reduced dispersion
US4076380A (en) * 1976-10-28 1978-02-28 Bell Telephone Laboratories, Incorporated Graded index optical fiber
WO1992010014A1 (en) * 1990-11-30 1992-06-11 Nkt A/S A method and apparatus for amplifying an optical signal
US5287373A (en) * 1992-08-17 1994-02-15 Alliedsignal Inc. Gradient doped solid state laser gain media
US6937636B1 (en) * 1999-09-27 2005-08-30 The Regents Of The University Of California Tapered laser rods as a means of minimizing the path length of trapped barrel mode rays
US6624925B2 (en) * 2001-03-13 2003-09-23 Textron Systems Corporation Optical amplifier employing an active doped unitary amplifier

Also Published As

Publication number Publication date
GB1269103A (en) 1972-04-06
FR2023459A1 (cg-RX-API-DMAC7.html) 1970-08-21
DE1955963A1 (de) 1970-10-15
NL6917219A (cg-RX-API-DMAC7.html) 1970-05-20

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